Download Q.25. Draw a plot of binding energy per nucleon (BE/A) vs. mass

General instructions :
(i)
(ii)
(iii)
(iv)
All questions are compulsory.
There are 30 questions in total. Questions 1 to 8 carry one marks each,
questions 9 to 18 carry two marks each, questions 19 to 27 carry three marks
each and questions 28 to 30 carry five marks each.
There is no overall choice. However, an interval choice has been provided in
one question of two marks, one question of three marks and all three
questions of five marks. You have to attempt only one of the given choice in
such questions.
Use of calculators is not permitted.
Q.1. Define the term ‘magnetic declination’.
(1)
Q.2. Why is small ozone layer on top of the stratosphere crucial for human survival?
(1)
Q.3. The three colored bands, on a carbon resistor are red, green and yellow respectively. Write the
value of its resistance.
(1)
Q.4. Point out ‘right’ or ‘wrong’ for the following statements :
(1)
(a) The mutual forces between two charges do not get affected by the presence of other charges.
(b) The potential, due to a dipole, at any point on its axial line, is zero.
Q.5. An a.c. current, I=I0 sin 𝜔t, produces a certain heat, H, in a resistor R, over a time T= 2π/𝜔. Write the
value of the d.c. current that would produce the same heat, in the same resistor, in the same time. (1)
Q.6. The diagram, given below, shows the refraction of a plane wave front, incident on the surface PP’
separating two media, (1)and(2). Which of the two media is the rarer one?
(1)
Q.7. State the relation between the frequency, 𝑣, of radiation, emitted by a LED, and the band gap
energy, Eg’ of the semiconductor used to fabricate it.
(1)
Q.8. “The ionospheric layer, in the atmosphere, is known to cause bending of e.m. waves so that they
get directed towards the Earth.” Name this mode of propagation of e.m. waves.
(1)
Q.9. Two charges +Q and –Q are kept at (-x2,0) and (x1,0) respectively in the xy – y plane. Find the
magnitude and direction of the net electric field at the origin (0,0).
(2)
Or
Draw the shapes of the suitable Gaussian surfaces, while applying gauss’s law to calculate the electric
field due to
(a) A uniformly charged long straight wire,
(b) A uniformly charged infinite plane sheet.
(2)
Q.10. Identify the different types of e.m. radiations, which are used
(a) to kill germs,
(b) for physical therapy.
(2)
Q.11. A cyclotron, when being used to accelerate protons
(mass=1.67x10-27kg, charge = 1.6x10-19C) has a magnetic field of (π/2) tesla applied normal to the plane
of its Dees. What must be the value of the frequency of the applied alternating electric field to be used
in it?
(2)
Q.12. Two concentric circular coils, one of small radius r1 and the other of large radius r2, such that r1<<r2
are placed coaxially with centers coinciding. Obtain the mutual inductance of the arrangement.
(2)
Q.13. Write two characteristics of equipotential surfaces. Draw the equipotential surfaces due to an
electric dipole.
(2)
Q.14. “A communication satellite is essentially a repeater station in space.” Justify this statement by
analyzing the function of a repeater.
(2)
Q.15. Write Einstein’s photoelectric equation relating the maximum kinetic energy of the emitted
electron to the frequency of the radiation incident on a photosensitive surface. State clearly the basic
elementary process involved in photoelectric effect.
(2)
Q.16. The figure shows a ‘double slit experimental set-up’, for observing interference fringes due to
different component colures of white light. What would be the predominant colures of the fringes
observed at the point.
S1
P
S
O
S2
D
(i)
O, the central point
(ii)
P, where S2P-S1P= 2 ?
𝜋𝑏
(Here 𝑛b is the Wavelength of the blue colour)
(2)
Q.17. A message signal of frequency 10 kHz and peak voltage of 10 volts is used to modulate a frequency
of 1 MHz and peak voltage of 20 volts. Determine(i) modulation index, (ii) the side bands produced. (2)
Q.18. Crystal diffraction experiments can be performed either by using electrons accelerated through
appropriate voltage, or by using X-rays. If the wavelength of these probes(electrons or X-rays) is 1 A,
estimate which of the two has greater energy.
(2)
Q.19. A system capacitors, connected as shown, has a total energy of 160 mJ stored in it. Obtain the
value of the equivalent capacitance of this system and the value of Z.
(3)
10µF
7µF
15µF
3µ F
(Z) µF
+
-
Q.20. State, with the help of a circuit diagram, the working principle of a potentiometer. Describe briefly
the method used for determining the internal resistance of a cell.
Draw also the necessary circuit for it.
(3)
Q.21. Three resistors, R1, R2 and R3 are connected in a parallel, across a source of emf E and negligible
internal resistance
Obtain a formula for the equivalent resistance of this combination. Also write expressions for the
current through each of the three resistors.
(3)
Q.22. The inputs, A and B, shown here, are used as the inputs for three different gates, G1, G2, and G3.
The outputs, obtained in the three cases, have the forms shown.
Identify the three gates and write their truth tables.
(3)
Q.23. The velocity of a certain monochromatic light, in a given transparent medium, is 2.25 x 108 ms-1.
What is the (a) critical angle of incidence, (b)polarizing angle for this medium?
(3)
Q.24. The energy of the electron, in the ground state of hydrogen,is-13.6 eV. Calculate the energy of the
photon that would be emitted if the electron were to make a transition corresponding to the emission
of the first line of the
(i) Lmen series
(ii) Balmer series
Of the hydrogen spectrum.
(3)
Q.25. Draw a plot of binding energy per nucleon (BE/A) vs. mass number (A) for a large number of nuclie
lying between 2 ≤ A ≤ 240. Using this graph explain clearly how the energy is released in both the
processes of nuclear fission and fusion.
(3)
Q.26. State the principle of a transistor amplifier with positive feedback working as an oscillator. Draw a
circuit diagram showing how the feedback can be achieved by induction coupling (through mutual
inductance) to get a self-sustained oscillator. Explain briefly it’s working.
(3)
Or
How is a zener diode fabricated so as to make it a special purpose semiconductor diode? Draw the
circuit diagram of a zener diode as a voltage regulator and explain its working.
(3)
Q.27. When a ray of light passes through a triangular glass prism, find out the relation for the total
deviation , 𝛿, in the terms of the angle of incidence,𝑖, and angle of emergence 𝑒. Plot a graph showing
the variation of angle of deviation with the angle of incidence and obtain the condition for the angle of
minimum deviation.
(3)
Q.28. Write an expression for the force experienced by a charge 𝑞, moving with a velocity →, in a
𝑣
magnetic field →. Use this expression to
𝐵
(i) define the unit of magnetic field.
(ii) obtain an expression for the force experienced by a current carrying wire in a magnetic field.
Using the result obtained in (ii) above, along with the (well-known) expression for the magnetic field due
to a long straight current carrying wire, deduce the expression for the force between two long straight
parallel wires carrying currents I1 and I2 in the same direction.
(5)
Or
Deduce the expression for the torque acting on a rectangular current loop placed in a uniform magnetic
field. If → represents the magnetic moment of the current loop and → the magnetic field, shows that
𝑚
𝐵
the torque → can be expressed as
𝜏
→ = →x→,
𝜏
𝑚 𝐵
Indicating clearly the direction in which the torque acts with respect to the directions of → and → .
𝑚
𝐵
Explain briefly how the working of a moving coil galvanometer is based on this principle.
(5)
Q.29. An a.c. source of emf E=E0 sin 𝜔𝑡 is connected across a series combination of an inductor L, a
capacitor C and a resistor R. obtain an expression for the equivalent impedance (Z) of the circuit and
hence find the value of 𝜔, for the a.c. source, for which Z=R.
Show that the phase angle, ∅,(between the current flowing in this circuit and the voltage applied to it)
can be obtained through the relation
𝑅𝑒𝑎𝑐𝑡𝑖𝑣𝑒 𝑖𝑚𝑝𝑒𝑑𝑎𝑛𝑐𝑒
].
𝑅𝑒𝑠𝑖𝑠𝑡𝑎𝑛𝑐𝑒
∅= tan-1 [
(5)
Or
Explain, with the help of a necessary diagram, the working of a step-up transformer and obtaion the
expression for the transformer equation
Where the symbols have their usual meaning.
What are the two main assumptions made to derive the above relations?
Mention two important reasons due to which energy losses occur in actual transformer.
Q.30. (a) Draw the ray diagram for the formation of image of an object by a convex mirror and use it
(along with the sign convention) to derive the ‘mirror formula’.
(b) Use the mirror formula to show that for an object, kept between the pole and focus of a concave
mirror, the image appears to be formed behind the mirror.
(5)
Or
Draw a labeled ray diagram for the formation of image by a compound microscope. Obtain the
expression for the total magnification when the image is formed at infinity.
In the case of a compound microscope, give reasons to explain the following :
(i)
(ii)
Both the objective and the eyepiece have short focal lengths.
Our eyes should be positioned not on the eyepiece but a short distance away from it for
best viewing.
(5)